Generally, when a spinning reel is used to catch a fish, the handle is operated to rotate the rotary frame to wind up the line onto the spool the risk exists that the line, when subjected to a load overcoming the durability of the line, may be snapped.
Therefore, spinning reels generally incorporate into the reel body a drag mechanism comprising dragging members at the reel body side, dragging members at the spool shaft side, and a knob for adjusting both the dragging members in the amount of press-contact force which they make with each other, so that the knob is operated to give to the rotation of the spool shaft a desired resistance corresponding to the durability of the line.
The drag mechanism is adjustable of its dragging force applied to the spool via the spool shaft in a range of 0 to 100%, but the dragging force, when a ratio of variation thereof is made larger with respect to a quantity of operation of the knob, will be changed by a large amount even with a small quantity of operation of the same.
Accordingly, for example, when a hooked fish abruptly pulls the line, the knob is often operated to readjust the dragging force more than necessary, resulting in that the spool shaft being subjected to a dragging force overcoming the durability of the line or that it is excessively weakened.
In a case where a ratio of change in the dragging force with respect to the operational quantity of the drag knob is reduced, an abrupt change is not created in the dragging force even when the drag knob is operated to a somewhat large extent.
Hence, when the dragging force of the drag mechanism is adjusted, a problem such that a dragging force overcoming durability of the line is given to the spool shaft, or the dragging force is reduced too much, is eliminated, but a problem is created in that rapid adjustment is not possible.